What exactly is bicameral mind?

The phrase comes from the book "The Origin of Consciousness in the Breakdown of the Bicameral Mind" by Julian Jaynes. In it, he expounds on his theory that in early man, the two halves of the brain did not communicate because the means of that communication is the spoken word (conscious thought in human language). So after language written and spoken comes into being, the bicameral mind (the right and left halves of the brain only connect through a nerve bundle called the 'corpus collosum') starts to 'speak' so that a person begins to 'hear' thoughts' He further speculates that it is these articulate thoughts from within our own brains were the voice(s) of (the) god(s).

In Westworld, they are using this theory as the basis of how to control/program the robots into a higher level of consciousness by having a voice 'speak' to them as if it is outside their own mind - the voice of god as Jaynes thought of it.